Reversing pneumatic amplifier

ABSTRACT

There is disclosed a reversing pneumatic amplifier including a valve ball movable in a sleeve for opening or closing a control slot provided circumferentially in the sleeve in a radial plane thereof. The valve ball is displaced in one or the other direction when a pilot pressure, indirectly exerting a force to the ball through a bellows and a push rod, exceeds or drops below a predetermined value. Said force is opposed by a supply pressure directly affecting the valve ball. Dependent upon the direction of displacement of the valve ball, the output pressure of the amplifier is either increased or decreased.

United States Patent 1 Otteni I REVERSING PNEUMATIC AMPLIFIER HermannOtteni, Forchheim, Germany [75] lnventor:

[73] Assignee: Siemens Aktiengesellschait, Munich,

Germany [22] Filed: Aug. 13, 1971 [21] App1.No.: 171,569

[30] Foreign Application Priority Data 51 Jan. 16, 1973 PrimaryExaminer-Henry T. Klinksiek Assistant ExaminerRobert J. MillerAtt0rney-Edwin E. Greigg [57] ABSTRACT There is disclosed a reversingpneumatic amplifier including a valve ball movable in a sleeve foropening or closing a control slot provided circumferentially in thesleeve in a radial plane thereof. The valve ball is displaced in one orthe other direction when a pilot pressure, indirectly exerting a forceto the ball through a bellows and a push rod, exceeds or drops below apredetermined value. Said force is opposed by a supply pressure directlyaffecting the valve ball. Dependent upon the direction of displacementof the valve ball, the output pressure of the amplifier is eitherincreased or decreased.

4 Claims, 1 Drawing Figure V l. T ,3

REVERSING PNEUMATIC AMPLIFIER BACKGROUND OF THE INVENTION This inventionrelates to a reversing pneumatic amplifier in which a movable controlmember, guided in a sleeve, opens or closes control openings. One sideof the movable control member is exposed indirectly to a pilot pressure,while its other side is affected directly by a supply pressure.

Amplifiers of the aforenoted type find application particularly inpneumatic controllers wherein a force balance controls a nozzle andflapper system which in turn delivers the pilot pressure for theamplifier. By virtue of the forces to which the movable control memberis exposed, the control openings are closed for a predetermined pressurevalue of the input pressure. In case the input pressure exceeds thepredetermined value, the output pressure chamber is connected with adischarge opening and if the input pressure decreases, communication isestablished between an auxiliary energy source and the output pressurechamber.

Known amplifiers of the aforenoted type have a plurality ofinterconnected pistons as movable control members, the edges of whicheffect the control of the auxiliary energy source as they slide over oruncover the control openings in their cylinder. Such movable pistonvalves are expensive and are difficult to manufacture and further, thereis significant wear because of the substantial area of contact betweenthe pistons and the cylinder.

In another known type of pneumatic amplifiers balls are used as themovable control members. Such balls are easy to manufacture and, unlikethe pistons, do not have a tendency to jam. These balls, however,cooperate with control edges rather than with control openings.Consequently, the manufacture of the guide cylinder which has to beprovided with steps or extensions forming the control edges is quitecomplex.

In known amplifiers a plurality of movable control members, such aspistons or balls, are combined with one another or with valve bodies andare interconnected by means of linkages or the like. Such arrangementsare prone to substantial switching errors because the valve bodiesactuated by the movable control members have to be lifted from the valveseats.

It is further known to use, for the indirect actuation of the movablecontrol members by the pilot pressure, a membrane or a spring bellowswhich affects the movable control member directly or through a linkagemechanism. Since the supply pressure is usually by one order ofmagnitude larger than the pilot pressure, the movable control body maybe held in a predetermined position by the opposing pressures of thesurface ratios between the control body on the one hand and the membraneor the bellows on the other hand are properly chosen.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention toprovide an improved reversing pneumatic amplifier which requires smallspace, is of simple structure, consumes low auxiliary energy with highoutput and operates with no switching errors.

Briefly stated, according to the invention, the movable control memberis constituted by a sole ball which is disposed in a cylindrical sleeveprovided, in a radial plane, with at least one slot forming a controlopening. The ball is controlled by means of a membrane or bellows and anactuator rod in such a manner that the output pressure chambercommunicates with the ambient atmosphere in case of increasing pilotpressure, while it communicates with the supply pressure source in caseof decreasing pilot pressure.

The invention will be better understood as well as further objects andadvantages of the invention become more apparent from the ensuingdetailed specification of a preferred, although exemplary embodiment ofthe invention taken in conjunction with the sole FIGURE illustrating theinvention in longitudinal section.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the FIGURE, aball 1 constituting a movable control member, is positioned and guidedin a bilaterally open-ended sleeve generally indicated at 2. The latterhas, in a radial plane, a circumferential slot 3 constituting a controlopening. The sleeve 2 is force fitted into a central opening of a baseblock 4. One end of the sleeve 2 communicates with an auxiliary energysource (not shown) delivering a supply pressure P while the other end ofthe sleeve 2 is connected with the ambient atmosphere through a channel5. To the base block 4 there is secured in a fluid-tight manner a cap 6which defines a chamber 7. In the latter there is disposed a bellows 8which separates the chamber 7 from the bellows chamber 9 which, in turn,communicates with the sleeve 2 and with the discharge channel 5. Thebellows 8 has a base plate 10 to which there is centrally secured anaxially displaceable push rod 11 by means of an externally threadedscrew portion 110. The push rod 11 is in contact with the ball 1 andtransmits thereto the force of the pilot pressure P which prevails inchamber 7 and which is admitted thereto through an inlet bore 12provided in the base block 4. The ratio between the cross-sectional faceof the ball 1 and the effective face of the bellows 8 is selected insuch a manner that for a predetermined value of the pilot pressure P(corresponding to the zero value of the characteristic amplifier curve)and for a predetermined value of the supply pressure P the ball 1 is sopositioned in the sleeve 2 that the equator of the ball is situated inthe middle of the slot 3, so that the latter is obturated by the ball 1.A fine axial adjustment of the push rod 11 may be effected by turningthe screw 11a.

This pneumatic amplifier is advantageously used in compensatingregulator systems; it becomes effective only when the pilot pressure Pdeviates from the predetermined value (zero point on the amplificationcurve). The drawing shows the ball 1 in its stable position; thus, theamplifier is in the zero point on its characteristic curve. Apart from avery small idling consumption caused by leakage losses, no energyconversion takes place. If the pilot pressure P exceeds thepredetermined value, then the ball 1 is displaced downwardly by the pushrod 11 and, as a result, the slot 3 is partially or entirely exposed.Since the slot 3 provided in the control sleeve 2 communicates throughan annular chamber 13 with the output opening 14 of the amplifier, theoutput pressure P will drop since the annular chamber 13 will nowcommunicate through the slot 2 with the discharge channel 5. Thiscondition will last in a compensating system until the pilot pressure Pagain reaches its predetermined value. If, on the other hand, the pilotpressure P drops below the predetermined value, then the supply pressureP displaces the ball 1 upwardly. In this case, communication will beestablished between the auxiliary energy source delivering the supplypressure P and the output opening 14 of the amplifier. As a result, theoutput pressure P A will increase. It is thus seen that during operationof the amplifier, consumption of auxiliary energy (utilization ofpressure P takes place only when the output pressure P is to beincreased.

The sleeve 2 is preferably formed of two similar cylindrical parts 21and 22 force fitted in a fluid-tight manner in the base block 4 andarranged slightly spaced and in axial alignment with respect to oneanother. The width of the circumferential slot 3 is thus determined bythe spacing between the two parts 21, 22 and the slot itself is definedby adjoining radial edge faces of these two parts which, in theirarrangement, are mirror images of one another. In this manner it ispossible to obtain a very narrow slot which has significant advantagesin enhancing a compact structure and a minimum consumption of energy inthe stable position of the ball 1. On the other hand, the uninterruptedcircumferential configuration of the slot 3 permits a relatively largeflow rate and thus results in a large amplifier output. In order toreduce the idling consumption of energy to 10 percent or less of themaximum flow rate, the diameter of the ball 1 should preferably be 20 30times larger than the width of the slot 3. For example, the slot widthmay be 0.25 millimeter and the ball diameter 5.5 millimeter. in case ofamaximum amplifier output of approximately 50 lit./min., the idlingconsumption will be about 5 lit./min. The external dimensions of thisamplifier which, as it may be observed from the drawing, comprises veryfew parts and is of very simple structure, are comparatively very smalland may be, for example, 24 X 24 X 20 millimeters.

In order to protect the amplifier from damages in case of overloadinginto one end of the sleeve 2, there is inserted a ring 15, the internaldiameter of which is smaller than that of ball 1, so that in case of aninterruption in the delivery of the supply pressure P the ball 1 will beseated thereon. On the other hand, the cap 6 is arranged at such adistance from the base plate 10 of the bellows 8 that the base plate 10,in case of an overload, will come into a face-to-face engagement withthe inner face of the cap 6.

It is further noted that from the amplifier according to the inventionswitching errors are substantially eliminated, since the ball 1, whichin its zero position blocks the control slot 3, is, when displaced,entirely surrounded and carried by a leakage air flow, so that afriction (i.e., the source of said switching error) between the ball 3and the inner wall of the sleeve 2 can generally not occur.

What is claimed is: 1 A reversing pneumatic amplifier comprising: A. afirst input means through which a pilot pressure is introduced into saidamplifier, B. a second input means through which a supply pressure isintroduced into said amplifier, C. discharge channel means incommunication with the ambient atmosphere, D. an output opening,

E. a hollow cylindrical control sleeve having a first open endcommunicating with said discharge channel means and a second open endcommunicating with said second input means,

F. a slot provided in said sleeve and extending in a radial planethereof; said slot connecting the inside of said sleeve with said outputopening,

G. a valve ball movably disposed in said sleeve and adapted to assumefirst, second and third positions, in said first position said valveball closes said slot, in said second position communication isestablished between said second input means and said output opening, insaid third position communication is established between said dischargechannel means and said output opening, and

H. means in engagement with said valve ball and in communication withsaid first input means for transmitting said pilot pressure indirectlyto said valve ball, said pilot pressure being opposed by said supplypressure directly affecting said valve ball through said second inputmeans.

2. A reversing pneumatic amplifier as defined in claim 1, wherein saidmeans defined in (H) includes A. a bellows pneumatically separating saidvalve ball from said pilot pressure, and

B. a push rod secured to said bellows and in contact with said valveball.

3. A reversing pneumatic amplifier as defined in claim 1, including abase block; said sleeve is formed of two spaced and axially alignedsleeve parts fitted into said base block; said slot is constituted bythe clearance between said two sleeve parts.

4. A reversing pneumatic amplifier as defined in claim 1, wherein thediameter of said valve ball is 20 30 times larger than the width of saidslot.

1. A reversing pneumatic amplifier comprising: A. a first input meansthrough which a pilot pressure is introduced into said amplifier, B. asecond input means through which a supply pressure is introduced intosaid amplifier, C. discharge channel means in communication with theambient atmosphere, D. an output opening, E. a hollow cylindricalcontrol sleeve having a first open end communicating with said dischargechannel means and a second open end communicating with said second inputmeans, F. a slot provided in said sleeve and extending in a radial planethereof; said slot connecting the inside of said sleeve with said outputopening, G. a valve ball movably disposed in said sleeve and adapted toassume first, second and third positions, in said first position saidvalve ball closes said slot, in said second position communication isestablished between said second input means and said output opening, insaid third position communication is establisheD between said dischargechannel means and said output opening, and H. means in engagement withsaid valve ball and in communication with said first input means fortransmitting said pilot pressure indirectly to said valve ball, saidpilot pressure being opposed by said supply pressure directly affectingsaid valve ball through said second input means.
 2. A reversingpneumatic amplifier as defined in claim 1, wherein said means defined in(H) includes A. a bellows pneumatically separating said valve ball fromsaid pilot pressure, and B. a push rod secured to said bellows and incontact with said valve ball.
 3. A reversing pneumatic amplifier asdefined in claim 1, including a base block; said sleeve is formed of twospaced and axially aligned sleeve parts fitted into said base block;said slot is constituted by the clearance between said two sleeve parts.4. A reversing pneumatic amplifier as defined in claim 1, wherein thediameter of said valve ball is 20 - 30 times larger than the width ofsaid slot.